1. Field of the Invention
The present invention relates to an ultrasonic motor for use as, for example, an image vibration correcting unit of a digital camera or an actuator of an autofocus (AF) lens or the like.
2. Description of the Related Art
Generally, when a voltage is applied to a piezoelectric device of the ultrasonic motor, longitudinal vibration and flexural vibration are induced, thereby producing elliptical vibration (oscillation). The ultrasonic motor transmits this elliptical vibration to a driven body via a driver so as to drive the driven body by friction. In such an ultrasonic motor, the piezoelectric device, which constitutes a vibrator, is disposed uniformly in contact with the driven body. Consequently, stable driving is achieved. Thus, a highly accurate contact (assembly) arrangement precision of the piezoelectric device with respect to the driven body in the ultrasonic motor affects the driving characteristic of the ultrasonic motor greatly.
Such a contact arrangement configuration has been disclosed in, for example, U.S. Pat. No. 6,979,935. According to U.S. Pat. No. 6,979,935, a plurality of concave portions are disposed at a predetermined interval in the vicinity of, for example, vibration nodes of a vibrator. These concave portions are disposed in a direction (pitch direction) perpendicular to the moving direction (roll direction). A plurality of convex portions provided on a supporting member engage the plural concave portions.
This supporting member is pressurized in the direction of the vibrator so that a frictional member which is a driver disposed on the bottom face of the vibrator is brought into contact with a contact member which is the driven body at a desired pressure. Consequently, when a vibration is induced in the contact member by the vibrator, the contact member is driven by friction via the frictional member.
As for the friction drive by such a vibrator, its drive efficiency can be enhanced as the contact between the frictional member and the contact member is kept uniform.
However, the configuration disclosed in U.S. Pat. No. 6,979,935 has a freedom only in the pitch direction of the contacts between the frictional member and the contact member and the configuration is set to be capable of making “profiling” actions only in the same direction. That is, the contact between the frictional member and the contact member is along the pitch direction. Thus, if any manufacturing error or assembly error is generated in components, the accuracy of contact between the frictional member and the contact member is worsened. For this reason, high processing and assembly accuracy of the components is required, so that manufacturing work including the processing and assembly is very troublesome, which is a problem to be solved.